Amazon used Echo devices for all kinds of invasive purposes other than advertised. Tracking the bluetooth identifiers of nearby devices is small potatoes compared to other things they've done:

https://en.wikipedia.org/wiki/Amazon_Sidewalk

One of those purposes was to explicity use Echos for tracking purposes:

> Amazon’s partnership will allow it beef up its tracking network, called Sidewalk, by letting Tile and Level devices tap into the Bluetooth networks created by millions of its Echo products.

https://www.cnbc.com/2021/05/07/amazon-partners-with-tile-to...

My car shows "last seen" on its Bluetooth connections. The murderer in this case was an invited friend; it's hardly implausible he's connected to Bluetooth there.

> I'm interested in evidence that this type of data extraction took place.

That they obtained access to the Echo's internals via Amazon is evidence. It sounds like you want proof of a very particular bit of data being in it, which I'd guess the FBI etc. aren't going to provide here.

I don't think that is ever admitted into the public record or presented to a jury. An expert reviews it and prevents the conclusions. In the even that you had the knowledge to review it yourself, you're excluded from the jury as jurors aren't allowed to question means and methods.